Hydraulic Disconnect Apparatus and Method of Use

ABSTRACT

A hydraulic disconnect apparatus is disclosed for disconnecting a pipe string or coiled tubing string from a bottom hole assembly for drilling, work over, or plug and abandonment of oil and gas wells. Disconnection is accomplished by pumping a circulation ball from surface through the pipe or coiled tubing string until it lands on a seat inside the apparatus. Fluid pressure is then applied to shift a piston assembly within the apparatus, thereby allowing a series of balls to retract. The upper and lower portions of the apparatus can then be separated by applying a tensile force to the upper portion.

PRIORITY

This application claims priority to U.S. provisional application Ser.No. 61/695,710 filed Aug. 31, 2012 for Hydraulic Disconnect Apparatusand Method, the entire content of which is hereby incorporated byreference.

FIELD OF THE INVENTION

This invention pertains to downhole equipment for oil and gas wells.More particularly, it pertains to a hydraulic disconnect apparatus foruse on a wellbore pipe string such as a coiled tubing string and, moreparticularly, this invention relates to an apparatus for disconnecting apipe string from a bottom hole assembly (known as a BHA).

BACKGROUND OF THE INVENTION

During the drilling, work over, or plug and abandonment of oil and gasproducing wellbores, a variety of downhole tools can be attached to apipe or coiled tubing string and utilized to perform a variety offunctions within the wellbore. It is often desirable to disconnect atool from the pipe or coiled tubing string so that a tool may be left inthe wellbore when the pipe or coiled tubing string is removed. Othertimes, a tool may become stuck in the wellbore during wellboreoperations and the need arises to remove the pipe or coiled tubingstring from the wellbore, independent of the tool, so that the wellboremay be reentered with a fishing tool string in an attempt to free thestuck tool from the wellbore. For these reasons, a tool disconnectdevice must be utilized.

A variety of tool disconnect devices may be use. Many tool disconnectdevices employ a hydraulic tool disconnect mechanism that employ shearpins and collets in the disconnect mechanism. These tools suffer fromshortcomings ranging from premature shear pin failure to cracking ofcollet bodies induced by the assembly or disassembly process. Somehydraulic disconnect devices employ a piston or ball to effectuatepressure changes for disconnection and that ball is typically left inthe bottom sub portion of the hydraulic disconnect after the tool isdisconnected from the pipe or coiled tubing string. A ball left in thebottom sub may prevent an operator from subsequently circulating fluidthrough the bottom sub and hinder subsequent well operations. Othertypes of tool disconnect devices suffer from unreliable tooldisconnection or require high pressures in order to disconnect a toolfrom the pipe or coiled tubing string.

Consequently, there is a need for a hydraulic tool disconnectingapparatus having improved piston and collet configurations that willreliably disconnect a tool or BHA from a pipe or coiled tubing stringwithout the aforementioned negative attributes.

SUMMARY OF THE INVENTION

The present invention presents a new hydraulic disconnect apparatus tosatisfy the aforementioned needs. The disconnect apparatus is comprisedof an upper top sub member having a plurality of ball retaining pockets,a lower bottom sub housing member and a piston member preferablycomprised of two parts, and a plurality of balls. The piston member ispreferably configured with a lower support piston member and an uppercollet member. The bottom sub contains a plurality of internalindentations that correspond with the balls, preferably matching ornearly matching the radii of the balls. The collet member contains aninternal profile such that a circulation ball of a given size will seatand substantially block the circulation of fluid through the disconnectapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a representative embodiment of thehydraulic disconnect apparatus of Applicant's invention

FIG. 2 is an end view of the hydraulic disconnect apparatus shown inFIG. 1.

FIG. 3 is a longitudinal cross-sectional view showing the hydraulicdisconnect apparatus shown in FIG. 1 cut through lines F-F of FIG. 2.

FIG. 4 is an elevation view of the top sub member of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 5 is an end view of the top sub member of the hydraulic disconnectapparatus shown in FIG. 1.

FIG. 6 is a longitudinal cross-sectional view of the top sub member ofthe hydraulic disconnect apparatus shown in FIG. 1 cut through lines G-Gof FIG. 5.

FIG. 7 is a detailed view of a ball retaining pocket of the top submember of the hydraulic disconnect apparatus shown in FIG. 1.

FIG. 8 is an elevation view of the bottom sub member of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 9 is an end view of the bottom sub member of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 10 is a longitudinal cross-sectional view of the bottom sub memberof the hydraulic disconnect apparatus shown in FIG. 1 cut through linesthrough lines J-J of FIG. 9.

FIG. 11 is an end view of the support piston member of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 12 is an elevation view of the support piston member of thehydraulic disconnect apparatus shown in FIG. 1.

FIG. 13 is an elevation view of the collet member of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 14 is an end view of the collet member of the hydraulic disconnectapparatus shown in FIG. 1.

FIG. 15 is as longitudinal cross-sectional view of the collet member ofthe hydraulic disconnect apparatus shown in FIG. 1 cut through linesthrough lines K-K of FIG. 14.

FIG. 16 is an elevation view of the piston assembly of the hydraulicdisconnect apparatus shown in FIG. 1.

FIG. 17 is a longitudinal cross-sectional view of a wellbore showing thehydraulic disconnect apparatus of FIG. 1 attached to a pipe string.

FIG. 18 is a longitudinal cross-sectional view of the hydraulicdisconnect apparatus shown in FIG. 1 at the moment the circulation balllands on seat inside the collet member.

FIG. 19 is a longitudinal cross-sectional view of the hydraulicdisconnect apparatus shown in FIG. 1 after the piston assembly hasshifted into the released position.

FIG. 20 is a longitudinal cross-sectional view of the hydraulicdisconnect apparatus shown in FIG. 1 after complete separation from anattached pipe or coiled tubing string tool or BHA.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows an embodiment of the hydraulic disconnect apparatus (10) ofthe present invention. The apparatus (10) is configured so that it maybe threadably attached on a pipe string that has a central bore throughwhich fluid may be introduced so that it will extend longitudinallyalong the axis of the pipe string at a position above a downhole tool ora bottom hole assembly, sometimes referred to as a “BHA”. The apparatusto provide a means for hydraulically separating the tool of BHA from apipe string or a coiled tubing string should such a need arise.

In the configurations shown in FIGS. 1-3, the apparatus (10) has anupper end of the referenced by (20) and lower end referenced by (25) andis comprised of an upper tubular top sub member (5) and a lower tubularbottom sub member (15). The top sub (5) is configured for threadableattachment to a pipe string by the means of an upper threaded connection(40). The lower tubular bottom sub member (15) is configured forthreadable attachment to a downhole tool or BHA by the means of lowerthreaded connection 45). As shown in FIG. 1, Top sub (5) and bottom sub(15) are fitted together by interlocking splines or castle features (35)and (30) respectfully. These castle features aid in the transmission oftorque through the apparatus (10) during rotation of the pipe string.

FIG. 3, a longitudinal cross-sectional view of the hydraulic disconnectapparatus (10) on the section line F-F of FIG. 2, illustrates theposition of the components of apparatus (10) in a latched or connectedconfiguration. The top sub (5) and bottom sub (15) each have centralbores, (185) and (190) respectively, which are in communication with thecentral bore of the pipe string. The castle features (35) and (30) oftop sub (5) and bottom sub (15) are interlocked and abutting. Seal (65)prevents fluid from entering or exiting through the castle features (35)and (30).

Positioned within the top sub (5) and bottom sub (15) are a supportpiston (55) and a collet (50). The support piston (55) and coil t (50)are threadably connected by means of box connection (70) of collet. (50)and pin connection (180) of support piston (55). Support piston (55) andcollet (50) are axially aligned with top sub (5) and bottom sub (15).The annulus between collet (50) and the internal surface of top sub (5)is sealed b means of seal (80). The annulus between support piston (55)and the internal bore of bottom sub (15) is sealed via by means ofseal(s) (95). The combination of the support piston (55) and collet (50)will sometimes be referred to as piston assembly (200), as shown in FIG.16.

A plurality of attachment balls (60) arrayed in a series are located inball retaining pockets (150) along top sub (5). These balls (60) areurged radially outward by contact with the support piston (55) to extendor protrude from retaining pockets (150) into indentations or dimples(90) in bottom sub (15). The balls (60) prevent the top sub (5) frommoving in both axial and circumferential directions in relation to thebottom sub (15). Thus the balls (60) prevent the top sub (5) fromseparating from the bottom sub (15) due to tensile forces. The balls(60) also aid in the transmission of torque from the top sub (5) to thebottom sub (15) or vice versa.

The support piston (55) is configured with a shoulder (125) which abutsthe lower face (195) of top sub (5). The support piston (55) may besecured in this position via shear screw(s) (100) and by collet (50).Collet (50) can also be configured such that shear screw(s) (100) may beeliminated completely. Surface (110) of collet (50) is in contact withabutment surface (105) of top sub (5). Collet (50) holds the supportpiston (55) in the correct location to keep the balls (60) firmlypressed into dimples (90) in bottom sub (15), thereby keeping apparatus(10) in a connected configuration.

The top sub (5) of the hydraulic disconnect apparatus (10) is shown inFIGS. 4, 5 and 6. FIG. 4, an elevation view of the top sub (5), and FIG.6, a longitudinal cross section view of the top sub (5) along line G-Gof FIG. 5, illustrate the internal abutment face (105), ball retainingpockets (150), and recess (140). FIG. 7 shows the ball retaining pockets(150) in demarcation Detail H. Each ball retaining pocket (150) has aprotrusion (155) such as a lip or ring of material that forms a diametersmaller than that of ball (60). This protrusion (155) prevents the ball(60) from exiting the ball pocket (150) radially, in a direction fromthe center axis toward the outer diameter of the top sub (5) andprovides a means of retaining the balls (60) within the top sub (5)during assembly of apparatus (10).

The top sub (5) of apparatus (10) is not provided with and does notrequire a sub collet for load transfer. The collet (50) in disconnectapparatus (10) simply retains the piston assembly (200) in place so asnot to rely on shear screws as is the case with many current hydraulicdisconnect devices. Collets are necessarily utilized in the subs in manycurrent hydraulic disconnect devices to serve as tensile load bearingcomponents. When a tensile load is applied to a pipe string or coiledtubing string configured with these disconnect devices, the tensile loadapplied must be transferred through the collet members of the sub.Accordingly, the collets of such devices are subjected to repeatedtensile loads placed upon them during in normal wellbore operations,such as when the pipe string is jarred, and these repeated loadsincrease wear and tear on these disconnect devices and the risk ofpremature separation. Because the hydraulic disconnect apparatus (10)described herein does not utilize a collet as a load bearing member, thepipe string and the apparatus (10) may be repeatedly jarred duringoperations with the risk of premature separation of the BHA from thepipe string due to connection failure, such as shearing of the shear pin(or screw), significantly reduced.

FIGS. 8-10 show the bottom sub (15) of the hydraulic disconnectapparatus (10). As shown in FIG. 8, the exterior of bottom sub (15) iscomprised of the castle features (30) and connection (45). Four castlefeatures (30) are shown for clarity but any number of interlockingcastle features (30) may be utilized. These castle features (30) ma beeliminated all together without reducing the performance of thishydraulic, disconnect apparatus. Connection (45) is shown to be a pin(or male) connection, but may also be a box (female) connection.

FIG. 10, a longitudinal cross-sectional view of the bottom sub (15) ofthe hydraulic disconnect apparatus (10) along section line J-J of FIG.9, illustrates the interior of the bottom sub (15). Bottom sub (15) iscomprised of a plurality of dimples or indentations (90), shear screw(s)(100), and an optional recess (120). Dimples (90) are shown in astaggered orientation with four dimples per row but they may be in anyorientation with any number per row. This chosen number of dimples (90)and orientation are merely shown for clarity of the illustration. Shearscrew(s) (100) are optional and they ma be used as a secondary means ofretention of the support piston assembly (200) within the hydraulicdisconnect apparatus (10). The optional recess (120) may be provided asa means for engaging and disengaging the bottom sub (15) to a frequentlyutilized fishing tool known as a “GS” pulling tool after the bottom sub(15) has been left in a wellbore. Recess (120) provides no benefit tothe connection or separation of the top sub (5) relative to the bottomsub (15).

The support piston (55) of the hydraulic disconnect apparatus (10) isshown in FIG. 11 and FIG. 12. FIG. 12, an elevation view of the supportpiston (55) illustrates the threaded connection (180), the plurality ofball recesses (85), and shoulder (125). Threaded connection (180) isprovided as a means of connection to the collet (50). The ball recesses(85), preferably elongated or ramped recesses, provide a means or spaceto allow the balls (60) to retract inwardly from the dimples (90) thatare located inside the bottom sub (15). When the support piston (55) andcollet (50) are shifted downward from the position shown in FIG. 2,support piston (50) will roll along the balls (60) moving the rampedrecesses (85) so that the balls will move radially inward from thebottom sub (15) to disengage the top sub (5) and allow separation of thetop sub (5) portion from the bottom sub (15). This process is shown inmore detail in FIG. 18 through FIG. 20.

FIGS. 13-15 show the collet (50) of the hydraulic disconnect apparatus(10). The collet (50) is comprised of a latching shoulder (110), aplurality of splits or slots (115) creating collet fingers (115 a) andabutment shoulder (130). While the collet (50) is shown to have sixslots (115) to recreate collet fingers (115 a) however, any desirednumber greater than one may be utilized. The amount of force required todownwardly shift the support piston (55) while collapsing the collet(50) can be varied by altering the number and or length of slots (115)as well as the thickness of each of the collet fingers (115 a). Thisforce can be adjusted to suit the particular application.

FIG. 15 is a longitudinal cross-sectional view of the collet (50) of thehydraulic disconnect apparatus (10) cut along section line K-K of FIG.14 showing the latching shoulder (110), splits or slots (115), colletabutment shoulder (130), circulation ball seat (175), and box connection(70). FIG. 16 illustrates the support piston assembly (200) with thesupport piston (55) is threadably engaged. to the collet (50). Theabutment shoulder (130) of collet (50) limits axial travel of thesupport piston (55) upon separation of the support piston assembly (200)from top sub (5) to place the support piston recesses (85) in thecorrect location to allow the balls (60) to retract. It also preventsthe support piston assembly (200) from exiting the top sub (5) uponseparation. This assures that all upper components, including thecirculation ball, may be removed from the wellbore upon separationexcept for the bottom sub (15). This is an advantage as it allows anoperator to circulate through the bottom sub (15) and subsequentlythrough the BHA after separation.

In the typical hydraulic disconnect device only shear screws areemployed to retain a piston assembly in place. Use of the collet (50)gives the hydraulic disconnect apparatus (10) the ability to withstandrepeated jarring impacts without the potential for premature separationof the BHA. Another advantage of the collet (50) of disconnect apparatus(10) is that collet (50) does not have to be collapsed for assembly anddisassembly of the apparatus (10). Most hydraulic disconnect devicesutilize collets where the fingers of the collets must be collapsed inorder for the tool to be assembled and disassembled. Stresses areinduced into a collet each time it is collapsed and this repeatedcollapsing can cause cracking in the fingers of the collet leading topremature failure.

For assembly of the hydraulic disconnect apparatus (10), the balls (60)are first inserted into the ball retaining pockets (150) of top sub (5)until balls (60) contact pocket protrusions (155). After all balls (60)are in place, the support piston (55) is inserted into the lower end oftop sub (5) with the ball recesses (85) aligned with the balls (60).Insertion continues until shoulder (125) abuts lower face (195). Collet(50) is then inserted into top sub (5) and box connection (70) ispartially threadably engaged to pin connection (180). The support piston(55) must be repositioned downward such that the balls (60) are fullyretracted. The top sub (5) along with the partially threaded pistonassembly (200) is then inserted into bottom sub (15) while interlockingcastle features (30) and (35) until it can go no further.

The piston assembly (200) is then shifted upward until shoulder (125)again abuts lower face (195). When the piston assembly (200) is shiftedupward the balls (60) will be pushed radially outward from the ballrecesses (85) and seated in the dimples (90) that are located inside thebottom sub (15). The collet (50) is then fully threaded to supportpiston (55) until tight. The shear screws (100) can now be inserted ifbeing utilized. The hydraulic, disconnect apparatus (10) is nowcomplete.

As shown in FIG. 17, the hydraulic disconnect apparatus (10) ispositioned and threadably attached to the down hole end (500) of a pipeor coiled tubing string (P) by means of upper threaded connection (40)at the top (20) of the top sub (5). A bottom hole assembly (BHA) is thenattached to the hydraulic disconnect apparatus (10) by means of threadedconnection (45) at the bottom (25) of sub member (15). The sequence ofconnection of the pipe or coiled tubing string (P) and the bottom holeassembly (BHA) to the hydraulic disconnect apparatus (10) may bereversed as desired. After such assembly the pipe or coiled tubingstring (P), with the attached hydraulic disconnect apparatus (10) andBHA, may be inserted into wellbore (WB) for use.

FIGS. 18-20 show the sequence of disengagement of the BHA from the pipeor coiled tubing string (P) by means of the hydraulic disconnectapparatus (10) described herein. When an operator desires to disconnectthe pipe string or coiled tubing string (P) from the BHA, a circulationball (100) of the correct size is pumped down the pipe string (P). Theball (100) will continue until it reaches the ball seat (175) inside thecollet (50).

FIG. 18 shows a longitudinal cross-sectional view of the hydraulicdisconnect apparatus (10) in the connected state with the balls (60)positioned in ball retaining pockets (150) of top sub (5), at the momentthe circulation ball (100) lands on seat (175) inside the collet (50).At this time the operator will see an increase in pump (circulation)pressure. The pressure will continue to increase until the hydraulicforces created from fluid pressure overcomes the force of the collet(50) holding the piston assembly (200) in place.

As shown in FIG. 19, the collet (50) will then be forced to collapse andthe entire piston assembly (200) will move downward until abutmentshoulder (130) of collet (50) encounters shoulder (135) of top sub (5).When the piston assembly (200) moves to this downward position, theballs (60) are aligned with recesses (85) of the support piston (55).This alignment allows the balls (60) to retract away from the dimples(90) of the bottom sub (15). It can be noted that seal (80) of thecollet (50) is now aligned with recess (140) of the top sub (5) thusallowing fluid to flow around the seal thereby relieving pump pressure.This decrease in pump pressure indicates to the operator that the pistonassembly (200) has shifted and the hydraulic disconnect apparatus (10)is ready for separation.

When a tensile load, is applied to the pipe string, the top sub (5) ofthe hydraulic disconnect apparatus (10) is separated from the bottom sub(5) as shown in FIG. 20. Upon such separation the top sub (5), pistonassembly (200), balls (60), and circulation ball (100) may then beremoved from the wellbore with the pipe string (P) and the bottom sub(15) with the still attached BHA is left behind.

1. A disconnect apparatus for disconnecting a pipe string from a bottomhole assembly comprising: (a) a tubular top sub member having an upperend, a lower end, a central bore through which a fluid may beintroduced, a collet engagement surface, a plurality of radiallyoriented ball retaining pockets, and an internal abutment shoulder; (b)a plurality of attachment balls extending from said ball retainingpockets of said top sub member; (c) a support piston assembly having anupper end, a lower end, a central bore through which a fluid may beintroduced, a collet section at said upper end, said collet sectionhaving an external abutment shoulder, and a piston section at said lowerend, said piston section having a plurality of ball recesses; (d) saidsupport piston assembly positioned within and releasably attached tosaid top sub member by means of said collet section and said colletengagement surface and configured to move upward and downward withinsaid top sub member upon release of said collet from said colletengagement surface of said top sub member, said downward support pistonassembly movement being restrained by said internal abutment shoulder ofsaid top sub member and said external abutment shoulder of said collet;(e) a tubular bottom sub member having an upper end, a lower end, acentral bore through which a fluid may be introduced, and a plurality ofinternal radially oriented dimples, said bottom sub member attached tosaid top sub member by engagement of said attachment balls within saidinternal dimples of said bottom member between said piston section andsaid bottom sub member; and (f) wherein downward movement of saidsupport piston assembly will move said attachment balls from saidinternal dimples of said bottom sub member into said ball recesses ofsaid piston section thereby releasing said bottom sub member from saidtop sub member.
 2. The disconnect apparatus recited in claim 1 whereinsaid upper end of said top sub member is attached to a pipe string andsaid lower end of said bottom sub member is attached to a bottom holeassembly.
 3. The disconnect apparatus recited in claim 2 wherein theintroduction of a desired pressure on said support piston assembly willrelease said collet section of said piston support assembly from saidcollet engagement surface of said top sub member thereby impartingdownward movement of said piston support assembly for releasing saidbottom sub member.
 4. The disconnect apparatus recited in claim 3wherein said desired pressure on said on said support piston assembly iscreated by a circulation ball obstructing said central bore of saidsupport piston assembly.
 5. The disconnect apparatus recited in claim 4wherein said top sub member and said bottom sub member abut betweeninterlocking splines.
 6. A disconnect apparatus for disconnecting a pipestring from a bottom hole assembly comprising: (a) a pipe string havingcentral bore through which a fluid may be introduced; (b) a tubular topsub member having an upper end, a lower end, and a central bore alignedwith said central bore of said pipe string through which a fluid may beintroduced, said upper end of said top sub member threadedly attached tosaid pipe string; (c) said top sub member having a collet engagementsurface and a plurality of radially oriented ball retaining pockets; (d)a plurality of attachment balls positioned in said ball retainingpockets of said top sub member; (e) a support piston assembly positionedwithin said top sub member, said support piston assembly having acentral bore aligned with said central bore of said top sub member, acollet section releaseably attached to said collet engagement surface ofsaid top sub member, and piston section having a plurality of pluralityof ball recesses, said support piston assembly and said top sub memberconfigured to limit axial travel of said support piston assembly withinsaid top sub member upon release of said collet from said colletengagement surface of said top sub member; and (f) a tubular bottom submember having a plurality of internal radially oriented dimples and acentral bore through which a fluid may be introduced, said bottom submember attached to said top sub member by confined engagement of saidattachment balls between said internal dimples of said bottom sub memberand said piston member wherein upon release of said collet from saidcollet engagement surface of said top sub member, said attachment ballswill disengage from said internal dimples of said bottom sub member andmove into said ball recesses of said piston section thereby releasingsaid bottom sub member from said top sub member.
 7. The disconnectapparatus recited in claim 6 wherein said bottom sub member is attachedto a bottom hole assembly.
 8. The disconnect apparatus recited in claim7 wherein a desired pressure on said support piston assembly willrelease said collet section of said piston support assembly from saidcollet engagement surface of said top sub member.
 9. The disconnectapparatus recited in claim 8 wherein said desired pressure on said onsaid support piston assembly is created by introduction of a circulationball into said central opening of said pipe string thereby obstructingsaid central bore of said support piston assembly.
 10. The disconnectapparatus recited in claim 8 wherein said top sub member and said bottomsub member abut between interlocking splines.
 11. In a pipe stringhaving a having a central bore containing a fluid column, a method fordisconnecting a pipe string from a bottom hole assembly comprising thesteps of: (a) providing a pipe string having a central bore containingto fluid column; (b) providing a tubular top sub member having an upperend, a lower end, and a central bore aligned with said central bore ofsaid pipe string, said top sub member having a collet engagement surfaceand a plurality of radially oriented ball retaining pockets; (c)providing a plurality of attachment balls positioned in said ballretaining pockets of said to sub member; (d) providing a support pistonassembly, said support piston assembly having a central bore alignedwith said central bore of said top sub member, a collect section, andpiston section having a plurality of plurality of ball recesses; (e)positioning said support piston assembly within said top sub member in amanner whereby axial travel of said support piston assembly within saidtop sub member is limited; (f) releasably attaching said collet sectionof said piston support assembly to said collet engagement surface ofsaid top sub member; (g) providing a bottom sub member having aplurality of internal radially oriented dimples and a central borethrough which a fluid may be introduced; (h) attaching said top submember to said bottom sub member in a manner whereby said attachmentballs are confined between said internal dimples of said bottom submember and said piston member and whereby upon release of said colletfrom said collet engagement surface of said top sub member, saidattachment balls will disengage from said internal dimples of saidbottom sub member and move into said ball recesses of said pistonsection thereby allowing said bottom sub member to be released from saidtop sub member; (i) attaching said bottom sub member to a bottom holeassembly; (j) running said pipe string and said attached bottom holeassembly into a wellbore; and (k) releasing said collet from said colletengagement surface of said top sub member thereby moving said supportpiston assembly and said attachment balls from said internal dimples ofsaid bottom sub member into said ball recesses of said piston section ofsupport piston assembly thereby releasing said bottom sub member fromsaid top sub member.
 12. The method as recited in claim 11 furthercomprising the step of applying tension to said pipe string.
 13. Themethod as recited in claim 12 wherein said step of releasing said colletfrom said collet engagement surface of said top sub member includes thestep of apply fluid pressure on said support piston assembly.
 14. Themethod as recited in claim 13 wherein the step of apply fluid pressureon said support piston assembly includes introducing a circulation ballinto said central opening of said pipe string thereby obstructing saidcentral bore of said support piston assembly.
 15. The method as recitedin claim 14 wherein the step of attaching said top sub member to saidbottom sub member includes abutting said top sub member and said bottomsub member between interlocking splines.
 16. The method as recited inclaim 15 wherein the step of positioning said support piston assemblywithin said top sub member in a manner whereby axial travel of saidsupport piston assembly within said top sub member is limited includesproviding interfacing shoulder surfaces on said top sub member and saidcollet of said support piston assembly.
 17. A disconnect apparatus fordisconnecting a pipe string from a bottom hole assembly comprising: (a)a pipe string having central bore through which a fluid may beintroduced; (b) a tubular top sub member threadedly attached to saidpipe string; said top sub member having a collet engagement surface anda plurality of radially oriented ball retaining pockets; (c) a pluralityof attachment balls positioned in said ball retaining pockets of saidtop sub member; (d) a support piston assembly haying a collet and apiston section having a plurality of plurality of ball recesses, saidsupport piston assembly releasably attached to said collet engagementsurface of said top sub member and positioned within said top sub memberto allow limited axial moment of said support piston assembly withinsaid top sub member; (e) a tubular bottom sub member having a pluralityof internal radially oriented dimples, said bottom sub member abuttingsaid top sub member with said attachment balls confined between saidinternal dimples of said bottom sub member and said piston memberthereby attaching said bottom sub member to said top sub member andwhereby downward movement of said support piston assembly will move saidattachment balls from said internal dimples of said bottom sub memberinto said ball recesses of said piston section of support pistonassembly thereby releasing said bottom sub member from said top submember; and (f) a bottom hole assembly attached to said bottom submember.
 18. The disconnect apparatus recited in claim 17 furthercomprising a means for obstructing said central bore of said supportpiston assembly and creating a desired pressure on said support pistonassembly thereby releasing said collet from said collet engagementsurface of said top sub member causing downward movement of said supportpiston assembly.
 19. The disconnect apparatus recited in claim 18wherein axial travel of said support piston assembly within said top submember is limit by interfacing shoulder surfaces on said top sub memberand said collet of said support piston assembly.
 20. The disconnectapparatus recited in claim 19 further comprising interlocking splinesbetween said top sub member and said bottom sub member.